The problem of providing safe aircraft flight is of current interest and includes a number of technological and organizational problems. One of such the problems is provision of safe flight when the determining factor is the aerodynamic influence of high level vortex turbulence, such as the wake vortices generated by another aircraft flying in the vicinity, as well as by the other objects, which undergo the airflows of high level of turbulence and vorticity.
It is well known that a moving aircraft generates wake vortices. An aircraft encountering wake vortices generated by another aircraft causes an important change in its angles of attack and slide. The aircraft is exposed the influence of air forces and moments that may throw it aside from the wake and while flying at low altitudes, for example during take-off and landing, such the factors may lead to hazard situations due to the failure of the aircraft to compensate the effect of such the forces by means of aircraft controls.
The appearance of aircraft with low aspect wings and with heavy wing loading causes the increase in wake vortex intensity that increases the danger for aircraft entering it.
A lot of research work on transport and decay of vortices shows that the ambient factors such as wind, windshift, stratification, and turbulence play an important role in these processes.
There is a potential opportunity to optimize the safety distances between aircraft during landing, take-off and cruise flight on the basis of plausible forecasting of wake vortex dynamics with due regard for now-casting of weather conditions and influence of atmospheric conditions, as well as for in-ground effects on the wake vortex dynamics.
One of the main trends for decision of this problem is the development of on board computer systems working in real time, determining the hazard level of aerodynamic influence on the aircraft, and permitting choice of the way of further correction of aircraft flight control aiming to compensate effectively such the aerodynamic perturbations.
Another task, which may be called an informational one, is the provision of the pilot with information on the location of wake vortices and the aircraft position with respect to wake vortices within the prediction period of time.
The method and device for visualization of wake vortices on a display on the basis of mathematical modeling taking into account the vortex generator aircraft and current weather data are well known. According to the technical solution, the device uses a fast-response display where simulated wake vortices generated by aircraft and located in the vicinity of the protected aircraft (U.S. Pat. No. 5,845,874, A) are visualized. However, in the case when there are many aircraft in the protected aircraft vicinity, for example near the aerodrome, the display will show a great number of simulated wake vortices, and it will be very difficult to identify which wake vortices are of real danger for the aircraft and which could be ignored.
One of the most perspective ways to increase the flight safety is to provide the pilot in real time with forecasted positions of wake vortices, entering into which may cause an incident.
The warning system against wake vortex turbulence is well known. The system is designed for onboard installation. It informs the aircraft crew on potential entry into wake vortices of another aircraft only when the system evaluates that the entry may occur after a certain period of time (U.S. Pat. No. 6,177,888, A). The system provides the mutual coordination of the both aircraft, exchange of warning signals and of information on the current altitude, distance and bearing, as well as tracking the wake vortex path with due regard for the local wind speed. The system determines the distance or the time before the aircraft enters into the wake vortices of another aircraft and indicates the aircraft approach to wake vortices when the distance or the time become less than the preset threshold. The width and the height of the wake vortex volume are calculated in each point of a set of points over the wake vortex path in the form of a function of distance from the given point to the neighboring aircraft.
However this system does not solve the problem of provision of the pilot with information on the hazard level when entering wake vortices and does not suggest the aircraft maneuver to avoid the entrance in wake vortices.
Moreover, the variety of aircraft flight conditions requires reduction of distances between aircraft, for example during the consecutive take-off or landing at aerodromes, which is very important for the increase of aerodrome capacity.
The reliable knowledge of position and structure of wake vortices and their effect on aircraft at the forecasted time will contribute to meet conflicting requirements for increase of flight efficiency and safety.
The warning system for wake vortices is well known. The system is designed for onboard installation and alerts the pilot on the predicted danger of another aircraft presence in the aircraft vicinity (U.S. Pat. No. 6,211,808, B1). The system consists of a spherical antenna made of dielectric material with eight sectors having receivers for detection of microwave signals reflecting from other aircraft. However the system is rather expensive and does not provide the pilot with information on the occurrence of hazardous air perturbations.
There exists the technical solution with respect to the scheme and method of preventing intersection of an aircraft with wake vortices of another aircraft (WO 00/71985). The solution requires determination of the position, geometry and structure of wake vortices generating by another aircraft, the presence of which is determined by means of information received from an airborne system of the first aircraft, from information received from another aircraft or from the aerodrome. The solution also requires determination of another aircraft altitude, forecasted position of another aircraft wake vortices with due regard for the ambient conditions, particularly the wind velocity and direction, air temperature, purification of the received data with the reference table, or modeling wake vortices with visualization of their location and path with respect to the first aircraft, forecasting the intersection point of the wake vortex path and the first aircraft trajectory, applying an alarm signal in the case where such crossing can occur. In general, the method is used to provide safety flight of two aircraft in the airport area. Its implementation can lead to the increase of the flight altitude for the first aircraft over the second one. The method uses the Traffic Collision Avoidance System. However, the first aircraft pilot receives the visualization of information on all vorticity areas in the flight area due to the presence of the second aircraft. Hence this situation does not give the true hazard picture of wake vortices to the pilot.
It is well known that the NASA, USA pays great attention for improving the terminal area efficiency, in particular during aircraft take-off and landing; and one of the research work trends is the implementation of the AVOSS (Aircraft Vortex Spacing System) that combines outputs of different systems and elaborate dynamic criteria of the safe wake vortex separations depending on weather conditions (37th Aerospace Sciences Meeting & Exhibit, Jan. 11-14, 1999, Reno, Nev., NASA Langley Research Center, Hampton, Va.). This system represents the current and forecasted weather conditions, models of transport of wake vortices and their decay in these weather conditions from the ground to the altitude of take-off and landing glidepath, as well as feedbacks the wake vortex behavior in real time. The wake vortex behavior is compared with the a priori determined sizes of the safety corridor and calculated data on the wake vortex decay. The result is the required safe aircraft separations. If wake vortices stay longer than it is expected, the reduction of the standard separations is prohibited. The wake vortex behavior is calculated for a number of ‘windows’ from the altitude of the glide path to the runway threshold.
However, this system has a number of restrictions such as: the lack of account of the altitude windshift, which may prevent wake vortex descent or originate wake vortex raising; the lack of account of a specific turbulence scale necessary for correct wake vortex decay modeling, and some other, which may lead to abnormal situations due to inconsistency of the calculated wake parameters provided to the flight controller with actual wake vortex parameters.
Moreover, the AVOSS implementation will lead to the increase of the load on the flight controllers that suffer heavy emotional burden due to intensification of their labor and can create undesirable risk of taking incorrect decisions.
One should bear in mind that foreign safety systems are mainly directed to the use of the so called ‘Instrument Flight Rules’ when aircraft flight control is carried out on the basis of the commands made by a flight controller and realized in the director or automatic mode.
However, the most critical juncture in the activity of flight controllers is making correct decisions in an emergency situation. There are two stages in that process: identification of the situation and determination of activities aiming to eliminate the emergency situation. Preliminary to each of activities, the flight controller should envisage the further steps. The perception of visual and voice signals in the verbal form from the long-term memory, from the display medium, or aurally needs a certain time under time deficiency. The time for perception of graphic symbols is far less and identification of the situation with indication of separate image zones permits to improve the decision adequacy.
Moreover, the effect of such a physical factor as acceleration causes the detraction of brain circulation of the pilot and can even force a brief loss of consciousness under emotional and nervous tension. Therefore, the rational way to solve the problem is the beforehand provision to a pilot or a flight controller of information in graphical symbols necessary for making a decision.